[Interferences between angiotensin-converting enzyme inhibitors and spinal anesthesia]

To determine whether angiotensine converting enzyme inhibition (ACEI) therapy should be continued up to the time of the surgical procedure, a standard practice for other modern antihypertensive agents, it should be known whether stopping the treatment does or does not lead to a hypertensive episode before surgery or at intubation and whether continuing treatment is or is not associated with an unacceptable fall in blood pressure at induction. Data from the literature obtained in patients chronically treated for essential hypertension with captopril or enalapril demonstrate that withdrawal of ACEI therapy before surgery does not result in a higher incidence of hypertensive episodes both preoperatively and at intubation. In contrast, an increased need for ephedrine to maintain blood pressure at induction is observed in patients who receive ACEI together with their premedication. This exaggerated hypotensive response to induction is in agreement with previous studies in anaesthetized subjects which have shown that angiotensin II contributes to hemodynamic regulation during general and epidural anaesthesia. It might also be the consequence of the specific effects of ACEI therapy on the loading conditions of the heart and/or the autonomic nervous system. It must be emphasized that both ACEIs and epidural anaesthesia dilate large arteries as capacitance vessels and increase vagal tone. The decreased tone in capacitance vessels accentuates the drops in blood pressure provoked by general or epidural anaesthesia through an increase in blood pooling at the expense of cardiac filling. This mechanism is enhanced by the presence of either a preoperative hypovolemia or a disturbed left ventricular diastolic function, which are two abnormalities frequently seen in hypertensive vascular surgical patients.(ABSTRACT TRUNCATED AT 250 WORDS)